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<html>
  <head>
    <meta charset='utf-8'>
    <meta name='viewport' content='width=device-width, initial-scale=1, user-scalable=no'>
    <meta name='mobile-web-app-capable' content='yes'>
    <meta name='apple-mobile-web-app-capable' content='yes'>
    <link rel='icon' type='image/png' sizes='32x32' href='../favicon-32x32.png'>
    <link rel='icon' type='image/png' sizes='96x96' href='../favicon-96x96.png'>
    <link rel='stylesheet' href='../css/common.css'>

    <title>Reference Space Invert</title>
  </head>
  <body>
    <header>
      <details id='details-panel' open>
        <summary>Reference Space Invert</summary>
        <p>
          Tests creating an offset reference space with the viewer pose, which
          should cancel out the pose. While a select event is engaged the viewer
          should appear locked at the origin looking directly at a checkmark
          image.
          <a class="back" href="./">Back</a>
        </p>
      </details>
    </header>
    <main style='text-align: center;'>
      <p>Click 'Enter XR' to see content</p>
    </main>
    <script type="module">
      import {WebXRButton} from '../js/util/webxr-button.js';
      import {Scene} from '../js/render/scenes/scene.js';
      import {Renderer, createWebGLContext, RenderView} from '../js/render/core/renderer.js';
      import {Gltf2Node} from '../js/render/nodes/gltf2.js';
      import {UrlTexture} from '../js/render/core/texture.js';
      import {ButtonNode} from '../js/render/nodes/button.js';
      import {QueryArgs} from '../js/util/query-args.js';
      import {mat4} from '../js/render/math/gl-matrix.js';

      // If requested, use the polyfill to provide support for mobile devices
      // and devices which only support WebVR.
      import WebXRPolyfill from '../js/third-party/webxr-polyfill/build/webxr-polyfill.module.js';
      if (QueryArgs.getBool('usePolyfill', true)) {
        let polyfill = new WebXRPolyfill();
      }

      // XR globals.
      let xrButton = null;
      let xrFloorSpace = null;
      let useInvertedSpace = false;
      let invertedReferenceSpace = null;

      // WebGL scene globals.
      let gl = null;
      let renderer = null;
      let scene = new Scene();
      scene.addNode(new Gltf2Node({url: '../media/gltf/cube-room/cube-room.gltf'}));
      scene.standingStats(true);

      let playButton = new ButtonNode(new UrlTexture('../media/textures/check-button.png'), () => {});
      playButton.translation = [0, 0, -0.5];
      scene.addNode(playButton);

      function initXR() {
        xrButton = new WebXRButton({
          onRequestSession: onRequestSession,
          onEndSession: onEndSession
        });
        document.querySelector('header').appendChild(xrButton.domElement);

        if (navigator.xr) {
          navigator.xr.isSessionSupported('immersive-vr').then((supported) => {
            xrButton.enabled = supported;
          });
        }
      }

      function initGL() {
        if (gl)
          return;

        gl = createWebGLContext({
          xrCompatible: true
        });

        document.body.appendChild(gl.canvas);

        function onResize() {
          gl.canvas.width = gl.canvas.clientWidth * window.devicePixelRatio;
          gl.canvas.height = gl.canvas.clientHeight * window.devicePixelRatio;
        }
        window.addEventListener('resize', onResize);
        onResize();

        // Set up a non-black clear color so that we can see if something renders wrong.
        gl.clearColor(0.1, 0.2, 0.3, 1.0);

        renderer = new Renderer(gl);
        scene.setRenderer(renderer);
      }

      function onRequestSession() {
        return navigator.xr.requestSession('immersive-vr', {
            requiredFeatures: ['local-floor'],
        }).then((session) => {
          xrButton.setSession(session);
          session.isImmersive = true;
          onSessionStarted(session);
        });
      }

      async function onSessionStarted(session) {
        session.addEventListener('end', onSessionEnded);

        initGL();
        scene.inputRenderer.useProfileControllerMeshes(session);

        session.updateRenderState({ baseLayer: new XRWebGLLayer(session, gl) });

        xrFloorSpace = await session.requestReferenceSpace('local-floor');

        session.addEventListener('selectstart', () => {
          useInvertedSpace = true;
        });

        session.addEventListener('selectend', () => {
          useInvertedSpace = false;
          invertedReferenceSpace = null;
        });

        session.requestAnimationFrame(onXRFrame);
      }

      function onEndSession(session) {
        session.end();
      }

      function onSessionEnded(event) {
        xrButton.setSession(null);
      }

      let tmpMat = mat4.create();
      function onXRFrame(t, frame) {
        let session = frame.session;

        let pose;

        if (useInvertedSpace) {
          pose = frame.getViewerPose(xrFloorSpace);
          invertedReferenceSpace = xrFloorSpace.getOffsetReferenceSpace(pose.transform);
          pose = frame.getViewerPose(invertedReferenceSpace);
        } else {
          pose = frame.getViewerPose(xrFloorSpace);
        }

        scene.startFrame();

        session.requestAnimationFrame(onXRFrame);

        scene.updateInputSources(frame, xrFloorSpace);

        scene.drawXRFrame(frame, pose);

        scene.endFrame();
      }

      // Start the XR application.
      initXR();
    </script>
  </body>
</html>
